Hydraulic lift truck



Feb. 25, 1964 R. E. KLEMICK ETI'AL 3,122,381

HYDRAULIC LIFT TRUCK Filed Aug. 16. 1960 6 Sheets-Sheet 1 4 FIG. 8 77 INVENTORS VRICHARD E. KLEMIcK By JOHN E. BUDRO ATTORNEY Feb. 25, 1964 R. E. KLEMICK ETAL 73,122,331

HYDRAULIC LIFT TRUCK Filed Aug. 16. 1960 6 Sheets-Sheet 2 INVENTOR.

RICHARD E. KLEMICK BY do: W0

-A- ATTORNEY Feb. 25, 1964 R. E. KLEMICK ETAL HYDRAULIC LIFT TRUCK 6 Sheets-Sheet 3 Filed Aug. 16. 1960 INVENTOR.

RICHARD E. KLEMICK JO N E. BUDRO BY W ATTORNEY Feb. 25, 1964 R. E. KLEMICK ETAL 3,

HYDRAULIC LIFT TRUCK Filed Aug. 16. 1960 6 Sheets-Sheet 4 IN V EN TOR.

RICHARD E. KLEMICK JOHN E. BUDRO Feb. 25, 1964 R. E. KLEMICK- ETAL HYDRAULIC LIFT TRUCK Filed Aug. 16. 1960 6 Sheets-Sheet 6 RESERVOIR ||4 FIG.|2

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RESERVOIR ,uos

FIG. l3 INVENTOR.

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ATTORNEY United States Patent 3,122,381 HYDRAULEC LIFT TRUCK Richard E. Klerniclr, Philadelphia, and John E. Budro, Mahanoy City, Pm, assignors to .lonard industries, inc, Grwigshurg, Pin, a corporation of Pennsylvania Filed Aug. 16, 1969, Ser. No. 49,911 3 Claims. (Cl. 28l43.23)

Our invention relates to a hydraulically powered lift truck.

One object of the invention is produce an improved truck of the type set forth.

A hydraulically powered truck. includes a platform, or fork, a plunger operatively connected to said platform, a reciprocating pump for raising said plunger to raise said platform, a handle for pulling or pushing the truck, means operatively connecting said handle to the piston of said pump whereby reciprocation of said handle operates the pump, and means for relieving the hydraulic pressure created by said pump to lower the platform.

It is therefore a further object of our invention to produce an improved lift truck of the type set forth in which the fluid pressure-reli ving means is carried by the upper end of the handle so as to be readily accessible, regardless of the position of the handle.

Since the upward movement of the plunger referred to is the result of the reciprocation of the truck handle, it follows that, when the plunger reaches the limit of its upward position, the handle cannot be moved from the position which it assumed at the end of the pumping, or plunger raising operation, until the hydraulic pressure sustaining the plunger in its uppermost position has been relieved. This may be satisfactory for lift jacks of the type used for raising one end of an automobile, but it is not satisfactory for trucks which are pushed or pulled from one place to another by the handle. This is due to the fact that even if the pressure were relieved just enough to lower the plunger out of contact with the mechanical stop which limits its upward movement, the first unintended reciprocal movement of the handle will actuate the pump piston and will again raise the plunger into contact with the mechanical stop referred to, and the handle will again be rendered immovable. To have to relieve the pressure every time tee handle is needed for pulling or pushing the truck, is altogether impractical.

It is therefore a still further object of the invention to produce improved means for automatically and continuously preventing the platform raising plunger from more than momentarily reaching the upper limit of its movement whereby the truck handle remains free for movement to a substantially vertical position for pushing, or to any other, angular, position for pulling the truck.

These and other objects are attained by our invention as set forth in the following specification and illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a lift truck embodying the invention, showing the fork, or platform, in its lower position.

FIG. 2 is an enlarged view, partly in elevation and partly in vertical section, looking in the direction of line 22. on FIG. 1.

FIG. 3 is an enlarged view, partly in section and partly in elevation, looking in the direction of line 33 on FIG. 2.

FIG. 4 is similar to FIG. 3, but showing a slightly modified construction and showing the truck platform in its raised position.

FIG. 5 is a side elevational view looking in the direction of line 55 on FIG. 1.

FIG. 6 is similar to FIG. 5, but showing the truck fork, or platform, in its upper position.

FIG. 7 is a reduced, sectional view taken on line 77 on FIG. 3 showing the position of certain parts with the truck platform in its raised position.

FIG. 8 is similar to FIG. 7 but showing the position of said parts with the truck platform in its lowered position.

FIG. 9 is a fragmentary side elevational view of the upper position of the operating lever showing the pressurerelief handle.

FIG. 10 is an exploded view showing various parts of the mechanism.

FIG. 11 is a partial section looking in the direction of line 1111 on FIG. 7.

FIGS. 12 and 13 are diagrammatic flow charts, more clearly to show the connections between various passages and valves.

The truck illustrated may include a solid platform or other support, but as shown, it includes a fork, the prongs it? of which are secured to, or are integral with, the opposite ends of the arms 14 of a yoke 12.

Pivoted to the opposite arms 14 of the yoke, as at 16, are bell crank levers, the vertical arms 29 of which are rotatable on pins 24, which are hereinafter referred to. FIGS. 1, 5 and 6. The horizontal arms 18 of the bell :crank levers are pivoted, as at 23, to the opposite ends of a casting 39, which is provided with a vertical bore 32 (FIG. 2) through which passes pendent extension 33 of pump body 34. The lower end of pendent extension 33 is solid and is provided with a bore 35 for receiving shaft 36 which carries main wheels 38. In order to compensate for irregularities in the surface on which the truck may be moved, bore 35 is flared outwardly as at 39, to provide play for shaft 36 sufiicient to compensate for slight iiregularities of the surface over which the truck is moved.

Pump body 34 is provided with ears 44, which carry fixed stub shaft 46 on which the lower end of truck handle 48 is pivoted. FIGS. 2, 3 and 4. Near the upper end of handle 4-3 is pivoted, as at 52, a pressure-relief lever 54, which will be hereinafter further referred to. FIG. 19. The lower end of handle 48 is provided with ears 5-15, which carry a pin 53 which carries roller 60. FIG. 10. As will be best seen from FIGS. 3, 8 and 10, roller 6% is confined between block 62 and the vertical arm 64 of an angle, the horizontal arm 65 of which is secured to block 62. Block 62 is provided with an opening for receiving the reduced end 66 of pump piston 68, FIGS. 1 and 10, of a conventional pump, said piston being secured to block 62 by pin 78, which engages opening 71 in block 62. and a hole 73 in said reduced end 6%, operatively to connect pump piston 63 to block 62, whereby rocking truck handle 43 in the direction of arrow 75, FIG. 1, reciprocates the pump piston 68. By this arrangement the arcuate movement of roller 60 is translated into horizontal reciprocation of piston 68. Piston 63 reciprocates in a chamber 86, FIG. 3, which communicates through passage 77 which is controlled by a ball check valve 76 with a fluid reservoir 74. FIGS. 12 and 13. Piston chamber Sit communicates through passage 84 and passage 86 which leads to the lower end of a chamber 88, which is formed in pendent extension 33 and in which reciprocates vertical plunger 98, the upper end of which is provided with a roller thrust bearing 91. On the suction stroke the piston moves to the right in FIG. 3, or away from the viewer in FIG. 11, to unseat ball valve 76 and draw fluid from reservoir 74. On the pressure stroke the pump piston re-seats ball valve 76 and unseats ball valve 82, against the tension of spring 83, to transmit fluid from piston chamber 811, through passages 84 and 86, to chamber 88 into chamber 80 through passage 77. By this arrangement, reciprocation of piston 68 by handle 48 creates pressure below plunger 90 to raise the latter, and hence, truck platform 18. It will be noted that when piston 68 is stationary, the static pressure in chamber 88 reseats ball valves 82 and 182 to maintain the pressure below plunger 80. In order to prevent ball valve 76 from closing passage 77, we provide adjustable stem 79 which limits the upward movement of the ball valve in response to the suction stroke of piston 68, as best shown in FIG. 11.

As the handle 48 of a truck of this type is used to reciprocate the piston pump, the hydraulic pressure against the pump piston binds the handle 48 in the last position to which it may have been moved during the pumping operation. This is not objectionable in the case of a jack used for raising a fixed load, such as one end of an automobile. But, immobilizing the truck handle is objectionable because the operating handle must be used for pulling, or for pushing, the truck. Nor will relieving the pressure by valve 54, or its equivalent, to keep the pressure within safe limits, serve the purpose because the pressure may still make the movement of the handle in pulling or pushing the truck dilficult or impossible. In order to prevent this immobilizing of the truck handle 48 of the present invention, means is provided for automatically and continuously relieving the hydraulic pressure to a limited extent, which is just enough to free the handle, but which does not appreciably lower the truck platform from the position to which it may have been raised. As shown in FIG. 3, plunger 90 is provided with a slidable sleeve 92 which is carried by pin 94, which is movable vertically in larger diameter bore 96. Pin 94 bears against the upper end of a rod 160, which is freely movable in passage 88 and which carries, or is adapted to bear down on, ball valve 102, which, in the presence of pressure in chamber 88, closes the lower end of passage 98. The pressure created in chamber 88 causes plunger 90 to move upwardly, or from the position of FIG. 3 to the position of FIG. 4. It will be noted that, when plunger 90 moves up to the position of FIG. 4, sleeve 92 abuts, and is arrested by, shoulder 184, While the plunger itself moves further upwardly. This causes pin 94 to push rod 190 downwardly enough to unseat ball valve 102. Unseating ball valve 182 permits fluid to pass from chamber 88 through passage 8 and through opening 96 into space 196 between the upper portion of plunger 90 and the wall of chamber 88 above seal 110. From space 186 the fluid flows through annular opening 109 to reservoir 74. The resultant decrease in the fluid pressure in chamber 88 allows plunger 88 and sleeve 92 to move downwardly, whereupon pin 84 resumes its floating relation to bore 96 and the fluid pressure in chamber 88 again moves ball valve 102 upwardly to close passage 98 to prevent further downward movement of plunger 91) and of truck platform carried thereby.

In the embodiment of FIG. 4, sleeve 92, pin 94, hole 96, passage 98, rod 1%, and ball valve 102 are omitted, and openings 188 are provided in the wall of chamber 88 leading to reservoir 74. As will be seen from FIG. 4, opening 188 is located in the upper portion of the wall of chamber 88, so that when plunger 91 moves to its uppermost position, opening 168 is exposed, and so that when the pressure below it is reduced, plunger 90 moves down to close opening 103 to stop further downward movement of plunger 91 In either embodiment, the momentary reduction in presure in chamber 88 is transmitted to piston chamber 89, and this permits movement of handle 48 to the desired truck pushing, or pulling, position. In other words, either of the pressure-relief mechanisms described permits some fluid to flow from chamber 88 back to reservoir 74. This lowers the plunger and provides room there above which, in turn, permits repeated reciprocation of pump piston 6-?) and thus permits repeated movement of the truck handle from pulling to pushing position, and vice versa, while the plunger is in its raised position.

To protect against overload we provide ball valve 114, which is tensioned to a position to close passage 116 by retainer 118 and spring 120. Spring 1219 is coiled about stem 122 and its pressure can be adjusted in any desired manner. It will be seen from FIG. 7 that passage 116 communicates with passage 84, which is connected through ball valve 82 with piston chamber 80, whereby, when ball valve 82 is unseated on the pressure stroke of piston 68, excess pressure in piston chamber unseats ball valve 114 and causes a predetermined amount of fluid to flow through passage 117, FIGS. 7, 12, 13, into reservoir 74.

In conventional lift jacks, such, for example, as those used to raise one end of an automobile, a handle similar to operating handle 48 herein is used for actuating the pump piston to raise the jack, and a separate mechanism is used for relieving the pressure to lower the jack.

According to our invention, we provide a pressure relieving mechanism which is operable from a point near the upper end of truck handle 48, so that it may be used without disengaging the hands from handle 48, by means of which the truck is being pushed or pulled. The pressure-relieving mechanism referred to includes an operating rod 126, which is connected, at its upper end, to previously mentioned lever 54, and is connected at its lower end to bracket 128. Rod 126 is adjustable by turnbuckle 127, or in any other suitable manner. FIGS. 1 and 10. Bracket 128 is provided with a pin 130, which engages a hole 131 in a block 132, which is welded or otherwise secured to car 56. Bracket 128 also has an oppositely projecting pin 134 which engages a cam slot or groove 136 formed in the periphery of a sleeve 138 which is freely movable on shaft 46. One end 156 of sleeve 138 is adapted to abut a pin 154, which is carried by a bracket 148 which is pivotally mounted on pump casting 34 by means of a pin 150 engaging a hole in said pump casting. FIGS. 3 and 7. Bracket 148 is provided with a surface 158 which is adapted to bear against the adjacent end of a plunger 16%. FIGS. 7 and 8. Plunger 160 is provided with a reduced stem 162, which is movable through a passage 174 in a bushing 164, and carries ball valve 166. Plunger 1611 and ball valve 166 are normally biased to the right, as viewed in FIGS. 7 and 8, by a spring 170 which bears against retainer 168 to keep passage 174 through bushing 164 closed. When bracket 148 is rotated in counterclockwise direction, as viewed in FIG. 8, plunger 160 is moved to the left and unseats ball valve 166 to permit fluid to flow through passage 174 to reservoir 74.

As shown in FIG. 10, previously mentioned pins 24 rotatably carry T-shaped sleeves 189, to which are secured the adjacent ends of rods 182, the opposite ends of which are secured to similar T-shaped sleeves 184. Sleeves 184 are rotatable about pins 186, which also rotatably carry brackets 188 which are fulcrumed at 1911 to the sides of prongs 1t) and which carry rollers 192. The purpose and operation of these parts are hereinafter set forth.

Pump housing 34 is provided with a lug, or plate, 209, against which truck handle 48 is adapted to hear when said handle is used for pushing, instead of for pulling, the truck.

If, for any reason, it is desired to reciprocate pump piston 68, such as by reciprocation of handle 48, without building any pressure in chamber 88, screw 89 is backed J off to allow fluid sucked into piston chamber 80 to flow, through passage 191, into reservoir '74. It is to be noted that this can be done before, or after, plunger 96 has been raised, and that it has no eifect on the position of the plunger.

The operation is as follows: To raise plunger 99, and hence yoke 12 and prongs 10, truck handle 48 is reciprocated in the direction of arrow 75 to actuate pump piston 68 through the instrumentality of cars 56, roller 6%, block 62, etc. When plunger 90 is raised, it raises yoke 12, and the truck platform, or prongs 19, will tilt. But, and as above described, raising yoke 12 correspondingly depresses roller 192 so as to keep the truck platform in a substantially horizontal position. It will be noted that the flaring of bore 35 for shaft 36, as at 3, compensates for irregularities in the surface of the floor on which the trucl is moved.

In the structure of FIG. 3, upward movement of plunger 90 causes sleeve 92 to engage shoulder 104, and further movement of plunger 96) causes pin 94 to depress rod 185) and unseat ball valve 102 to permit fluid to flow from chamber 88 through hole 96 and passage 1% to reservoir 74. In the structure of FIG. 4, upward movement of plunger 9%) uncovers opening 16% and permits fluid to flow from chamber 88 to reservoir 74, until the plun er moves down far enough to reclose openings 1%. The resultant lowering of fluid pressure in chamber 88, which communicates with piston chamber 30, permits further, limited reciprocation of handle 4-8 so that it may be moved into engagement with plate 269 to push the truck, or to an acute angular position to pull the truck.

T o relieve the pressure altogether, lever 54 is pulled up to rotate bracket 128, pin 134 of which engages cam slot 136 in sleeve 138 to move the latter in a direction to cause end 155 thereof to engage pin 154 of bracket 14%, fin er 158 of which will now bear against the end of plunger 160 to move the latter from the position of FIG. 7 to the position of FIG. 8, to permit fluid to pass from pressure chamber 38, through passages 84 and 86 and through passage 174 back to the reservoir. It will be seen that by this arrangement, pressure can be controllably relieved wholly, or partly, to lower platform 10, and that this can be done without taking the hands of the operator ofl cross bar 56 and regardless of the position of truck handle 48. The manner in which the overload mechanism, which includes spring 12% and ball valve 11 operates, is thought to be sufliciently clear, and is there fore not recapitulated at this point.

When yoke 12 is raised by plunger 9% the rear, right hand end of the truck, as viewed in FIGS. 1, 4 and 5, will be raised, and the platform, or prongs ill, will be tilted. But, due to the provision of hell levers 24 rods 132, brackets 18%, and rollers 192, the upward movement of yoke 12 depresses rollers 192, thus raising the front end of the platform to keep said platform horizontal.

To help overcome the weight of the handle and thus facilitate the pumping operation, pump piston 68 may be biased to the right, as viewed in FIG. 3, by a spring 69, the strength of which must be so limited as not to present siib stantial resistance during the pressure stroke of the pump piston.

To prevent handle 48 from moving to a horizontal position when the truck is not in use, ball valve 82 may be biased into its closing position by a spring 83, the strength of which is equal to, or very slightly greater than, the weight of the handle. This means that, unless force is applied to the piston to unseat ball valve 32 against the action of springs 69 and 83, piston chamber $3 will have enough liquid to prevent movement of the pump piston to the left, or in pressure producing direction, and therefore the truck handle cannot move down, or to the right, as viewed in FIG. 1.

To return lever 54 to its lower position after it has been pulled up to relieve the pressure, sleeve 138 is biased by a spring 139 in the direction of the arrow in FIG. 8, that is, in a direction opposite to the direction in which sleeve 138 is moved to rotate finger 158 into engagement with plunger 16% in the manner above described.

Piston chamber is preferably provided with a hole 81 which leads to reservoir 74 and serves as a vent and for admitting oil to lubricate the pump piston.

What we claim is:

1. A lift truck including a frame,

a push and pull handle pivotally connected, at a point above the lower end thereof, to said frame for arcuate movement about a horizontal axis,

a vertically disposed fluid pressure chamber,

a plunger connected to said frame and movable upwardly in response to fluid pressure there below,

a fluid reservoir,

a horizontal pump casing,

there being a vent connecting said reservoir and said casing,

a piston freely reciprocable within said casing and having one end thereof disposed outside said casing and in the path of movement of the lower end of said handle, and

means on the lower end of said handle and abutting said one end of said piston for translating arcuate movement of said handle into linear movement of said piston,

there being a passage leading from the pressure side of said pump casing to the lower end of said pressure chamber.

2. The truck defined in claim 1 and control means for automatically and continuously limiting the upward movement of said plunger, said control means including:

a vertical bore formed through the lower portion of the plunger and leading from the portion of said chamber below said plunger to the portion of said pressure chamber above said plunger,

a floating valve for closing the lower end of said passage in response to fluid pressure in the lower portion of the fluid pressure chamber,

a constantly open discharge opening leading from the upper portion of the fluid pressure chamber to said reservoir,

freely movable actuating means in said vertical passage and abutting said valve,

the weight of said valve and said actuating means being less than the upward fluid pressure exerted against said valve as long as the plunger is in a raised position,

and stop means disposed wholly within, and near the top of, said chamber and engageable with said actuating means when said plunger has moved to a predetermined upper position for depressing said valve into a non-closing position relative to said vertical bore to cause fluid to flow from the lower portion of the pressure chamber through said drain opening.

3. The truck defined in claim 1 and manually operable relief means for reducing the pressure in said fluid chamber to lower said plunger and said platform, said relief 0 means including:

a return passage leading from said fluid pressure chamber to said reservoir,

a valve in said passage and including a horizontal valve stem in said return passage with one end of said stem outside said passage, biasing means normally moving said valve to return passage-closing position,

a cam pivotally mounted adjacent said one end of said stem,

Z7 55 a vertical rod movable to an upper and to a lower Referenees Cited in the file of this patent position, with the upper end thereof near the upper UNITED STATES PATENTS end of said handle and with the lower end thereof 1 841 673 Raymond Jan 19 1932 ad acent sald ca fl 72 Bizzan'i Jan. 2, 1934 and means intermediate the lower end or said rod and 5 2 331 734 Schroeder Oct 12 1943 said cam and operable, upon upward movem nt of 2:413:761 Grower 1947 said rod to rotate and bring said cam into engage- 2,438,521 Barrett 22, 1949 ment with said end of said valve stem to move the 2,623,756 Elliott at al. Dec. 30, 1952 latter to return passage-opening position against the 2,940,767 Quayle June 14, 1960 action of the biasing means. 2,993,703 Paradise July 25, 1961 

1. A LIFT TRUCK INCLUDING A FRAME, A PUSH AND PULL HANDLE PIVOTALLY CONNECTED, AT A POINT ABOVE THE LOWER END THEREOF, TO SAID FRAME FOR ARCUATE MOVEMENT ABOUT A HORIZONTAL AXIS, A VERTICALLY DISPOSED FLUID PRESSURE CHAMBER, A PLUNGER CONNECTED TO SAID FRAME AND MOVABLE UPWARDLY IN RESPONSE TO FLUID PRESSURE THEREBELOW, A FLUID RESERVOIR, A HORIZONTAL PUMP CASING, THERE BEING A VENT CONNECTING SAID RESERVOIR AND SAID CASING, A PISTON FREELY RECIPROCABLE WITHIN SAID CASING AND HAVING ONE END THEREOF DISPOSED OUTSIDE SAID CASING AND IN THE PATH OF MOVEMENT OF THE LOWER END OF SAID HANDLE, AND MEANS ON THE LOWER END OF SAID HANDLE AND ABUTTING SAID ONE END OF SAID PISTON FOR TRANSLATING ARCUATE MOVEMENT OF SAID HANDLE INTO LINEAR MOVEMENT OF SAID PISTON, THERE BEING A PASSAGE LEADING FROM THE PRESSURE SIDE OF SAID PUMP CASING TO THE LOWER END OF SAID PRESSURE CHAMBER. 